1. Field of the Invention
The present invention relates to a method for unsticking a head/slider assembly stuck on the surface of a recording disk rotated by a drive motor, and relates to a disk drive device performing an operation for unsticking the head/slider assembly from the recording surface.
2. Description of Related Art
A hard disk drive device contains at least one magnetic recording disk, and data are stored on both surfaces of the magnetic recording disk. One read/write head is provided for each recording surface. The read/write head is mounted on a slider, and these are called a head/slider assembly. The head/slider assembly is mounted on the front end of a flexible support arm, the rear end of which is pivotally mounted on a frame of the hard disk drive device. The magnetic recording disk is rotated by a spindle motor, and the supporting arm which supports the head/slider assembly is rotated around a pivot point in a radial direction of the magnetic recording disk by a voice coil motor (VCM).
A contact start/stop (CSS) scheme or a load/unload scheme is used in the hard disk drive device. In the CSS scheme, the head/slider assembly is landed on a rest region or a non-recording region located inside the inner most recording track on the surface of the magnetic recording disk during a standby period, and takes off from the surface of the rest region when the magnetic recording disk is rotated.
In the load/unload scheme, a ramp element is mounted at a peripheral of the magnetic recording disk. A surface of the ramp element is ramped, and a front end of the head/slider assembly is moved by the VCM to ride on the ramped surface so that the head/slider assembly rests on the ramp element during the standby period.
In the CSS scheme, the head/slider assembly is contacted to the rest region by a bias force applied by the flexible support arm during the standby period. During the contact to the rest region, the head/slider assembly tends to stick to the rest region, so that the magnetic recording disk does not rotate when the spindle motor is activated to read or write the data.
Japanese laid open patent application 8-203193 discloses a technology for unsticking the head/slider assembly from the surface of the magnetic recording disk by moving the disk in both the forward and backward direction and moving the head/slider assembly in both the forward and backward direction. The movement of the forward and backward direction is called as an oscillation or a vibration. In the application, a natural oscillation frequency of the read/write head is stored in a memory, and both the spindle motor and VCM are vibrated at the natural oscillation frequency to unstick the head/slider assembly from the surface of the disk.
In the load/unload scheme, the head/slider assembly always flies above the surface of the magnetic recording disk. Since the head/slider assembly does not land on the surface of the disk, the surface of the disk can be polished to provide a smooth surface to reduce a flying height of the head/slider assembly, so that a data capacity is increased and a S/N ratio is improved.
Due to the reduced flying height, the head/slider assembly tends to stick on the surface of the magnetic recording disk during the read/write period. Since the head/slider assembly is moved across data recording tracks on the disk during the read/write period, the position at which the head/slider assembly sticks to the disk is unknown. A mechanical natural oscillation frequency of a mechanical system containing the magnetic recording disk, the head/slider assembly and the flexible support arm varies depending upon the position of the read/write head on the surface of the magnetic recording disk and the number of the stuck heads.
Another prior art technology unsticks the stuck head/slider assembly from the surface of the disk by steps of (1) selecting a frequency range f.sub.MIN -f.sub.MAX, which is selected on the assumption that a resonant frequency f.sub.0 exists in this frequency range, and selecting an amplitude of current applied to the spindle motor; (2) vibrating the spindle motor and the magnetic recording disk, that is, moving them in the forward and backward direction, at the frequency f.sub.MIN ; (3) vibrating the spindle motor and the magnetic recording disk at the frequency f.sub.MIN +.DELTA.f, by applying the selected amplitude of current of the frequency f.sub.MIN +.DELTA.f to the spindle motor; (4) vibrating the spindle motor and the magnetic recording disk at the frequency f.sub.MIN +2.DELTA.f, by applying the selected amplitude of current of the frequency f.sub.MIN +2.DELTA.f to the spindle motor; and (5) the above steps are repeated by increasing the frequency until the frequency reached the frequency f.sub.MAX.
This prior approach always changes the frequency of the vibration from the frequency f.sub.MIN to the frequency f.sub.MAX. It is apparent that it takes a long time period to reach from the frequency f.sub.MIN to the frequency f.sub.MAX.